In recent years, with the rapid development of digitization and high precision of the optical system, in the optical equipment such as digital camera, video camera and other photographic equipment as well as image playback (projection) equipment such as projector and projection television, higher and higher requirements are imposed on overall lightweight and miniaturization of optical system for reducing the number of optical elements like lens and prism therein. In the design of the optical system, the extensive use of high-refractivity glass or the use of non-spherical lens is applied to achieve miniaturization, ultra-thin and wide-angle, to realize lightweight and high-performance of optical system while easier to achieve color correction, thus high-refractivity low-dispersion glass research and development needs are gradually increased.
Early production of high-refractivity low-dispersion glass contains a large amount of Ta2O5. For example, CN1876589A discloses an optical glass with refractive index of 1.75-1.85 and Abbe number of 34-44, which contains more than 15% but less than 35% of Ta2O5. Tantalum is a scarce metal, and the use of Ta2O5 is extremely unfavorable for the product cost control, so the research and development objective of optical glass workers is to reduce or not use Ta2O5 in the high-refractivity low-dispersion glass composition.